1. Field of the Invention
The present invention relates to a novel material for solid electrolyte.
2. Description of the Related Art
In Li7La3Zr2O12 having a garnet type crystal structure, not only a tetragonal system but also cubic system is reported as a crystal system (R. Murugan et al., Angew. Chem. Int. Ed., 46, 7778 (2007)). In particular, the one having a cubic system is known to exhibit high lithium ion conductivity in the order of 10−4 S/cm. This material is expected to be used as a solid electrolyte material of an entire solid lithium ion battery because it has characteristics of excellent chemical stability, wide potential window, as well as high lithium ion conductivity. Therefore, research and development are advanced for a method for producing Li7La3Zr2O12 having a cubic system garnet type crystal structure (hereinafter, “cubic system garnet type Li7La3Zr2O12”), or a secondary battery or the like using the material.
For example, an entire solid lithium secondary battery is proposed that includes a cathode having a cathode active material; an anode having an anode active material including a lithium alloy containing at least one specified elements selected from the group consisting of Mg, Al, Si, In, Ag and Sn; and a solid electrolyte of garnet type oxide represented by a composition formula Li5+XLa3(ZrX, A2−X)O12 (wherein, A represents one or more elements selected from the group consisting of Sc, Ti, V, Y, Nb, Hf, Ta, Al, Si, Ga and Ge, and X satisfies 1.4≦X<2), interposed between the cathode and the anode (JP 2011-70939 A).
Besides the above, for example, as a material in which Al is added to Li7La3Zr2O12, there is known a ceramic material containing lithium (Li), lanthanum (La), zirconium (Zr), oxygen (O) and aluminum (Al), and having a garnet type or quasi garnet type crystal structure (JP 2011-51800 A).